oo problem

[Bruno Desthuilliers]

Tool69 a écrit :
> Hi,
> I've got a simple but difficult problem :
> 
> Suppose I've got a Paper class, on wich I can draw i.e a rectangle, a
> circle or whatever.
> 
> class Paper(...):
>     def __init__(self, paperx, papery):
>         self.paperx = paperx
>         self.papery = papery
>         ....
>     def draw(self, Primitive_Object):
>         ....
> class Rectangle(  ): <--- a Primitive_Object
>     ...
> 
> Now, inside my Rectangle class, I need to recover the Paper instance
> who called it (because I need the paper sizes to calculate something).
> I now I can use a global variable, say " _paper" and then, inside  my
> Paper.__init__() write something like this :
> 
> global _paper
> _paper = [paperx,papery]
> 
> But it has drawbacks : 

Indeed...

> what if I've got several Paper instances ?

class Paper(...):
 >         ....
     def draw(self, drawable):
         drawable.draw(self)

class Rectangle(  ): <--- a drawable
    ...
     def draw(self, drawing_surface):
       ...

Now consider whether you really need Paper.draw...

HTH